Device for testing visual acuity



R. A. SHERMAN DEVICE FOR TESTING VISUAL ACUITY April 9, 1940.

Filed Dec. 4*, 1935 N IT 1 zum 7 Patented `Apr. 9, 19404 DEVICE FORTESTING VISUAL ACUIIYV Reuel A. Sherman, Meadville, Pa., assignor toKeystone View Company, Meadville, Pa., a cor. porationof PennsylvaniaApplication December 4, 1935, Serial No. 52,797

' V5 claims. (o1. sai- 20) This invention is directed to improvements indevices for testing visual acuity. 'I'he usual apparatus employed forthis purpose has targets positioned at 20 feet from the person beingtested,

the targets having groups of characters of different sizes so that theperson treated may be tested as to his capacity to correctly distinguishthe characters of the diiferent size groups. The persons acuity is givena rating corresponding to a relative value given to the smallest size ofsymbol that can be correctly distinguished and designated by the person.It is common in such tests to present the targets to both eyes and toeach eye individually, the opthalmologist recording 15 the results andprescribing correction in a-ccordance with these-tests.

With the present method and devices, stereoscopic views are provided onwhich targets are formed, photographically graduated as to size,

20, to provide conditions corresponding to targets actually placed atthe Vdefinite distance usually .used for test purposes. In this way itis possible to provide an apparatus and method which may be used undervarying conditions, under some of which it would be impossible to useordinary ap paratus and, further, it is possible to perform testsimpossible with the ordinary apparatus.

' Features and details of the invention will more l fully appear in thefollowing specification and claims:

A preferred form of the devices exemplifying the invention isillustrated in the accompanying drawing as follows:

Fig. 1 shows a stereoscopic view having .elds in accordance withthe-invention.

Fig. 2 -shows a similar view, with a modication of one of the elds.

Fig. 3 is aview similar to Fig. 1, presenting a modification of one ofthe elds, the modified 40 elds in Figs. 2 and 3 being in reverserelation. Fig. 4 shows a plan view of a stereoscope. Fig. 5 shows a sideelevation of the same. Fig. 6 shows an elevation of one of the slides asviewed through the stereoscope. I marls the stereoscopic views orslides, these having the usual right and left companion fields l 2 and3. In bothelds there are similar targets 4. These are varied in size byplacing a series of the targets at predetermined distances from thecamera, when the views are taken, so as to give a definite predeterminedrelation to the sizes of the targets. In the actual views as ordinarily5s be readable by a person of normal acuity.v

practice it is made 1/mth of the actual sizeof-f the target commonlyused at 20 feet from the `point of observation. Preferably `thevariousftargets are photographically arranged so as to give related sizescorresponding. to the related 5.

sizes of the characters for the different groups now ordinarily used byOphthalmologists with targets placed at the usual 20 foot distance,'so 1I,

that visual' acuity of al person being tested maybe checked against theordinary tests -or records 1o made with targets and characters of denitespacing and sizes as commonly used.I v

In order that the person being tested may be checked as to the.possibility of distinguishing characters orl symbols of different'sizes, "each 15 y target is'provided with segregated areas. ,As shown inthe views presented, a series of squares Ei aresimilarly arranged lneachtarget. The preferred arrangement of these squares provides a centersquare, a square at the top, 'a square atA l20 the.bottom, and a squareat each 'side ofthe center square. A-dot .6 is placed in the center ofone square in each target. As shown inFig. l, corresponding targets inthe two elds rhave the same arrangement of dot's 6, thus in the'largest2g,

target the square at the right in bothfieldsfis 5 r providedwith theldot 6. In the second'target..

\ the square atthe left in both eldsis provided with a dot. In the-third target, lthe center square is provided with a dot in bothne1ds,ana this vso 'l shifting o`f the dot to diiIerent squares, asthetargets recede or become smaller in size, is car.- vried out. As-theseviews are presented to the` .f'person,v he is asked to locate the dotin` each target and this is carried forward to the smallest 35 target inwhich he can correctly distinguish the square in which the dot isplaced. In observing the view in Fig. 1, the person views the slide andsees the views in normal manner of observing such a View utilizingbotheyes,` and his capacity 40 y for correctly or incorrectly placingthe dot, establishes his Visual acuity with both eyesas'normally 'I'heviews .are used in an ordinary stereoscope.

as shown' in Figs. 4, '5 and 6, these stereoscopes 45 having lenses lmounted in a lens-carrying plate 8. .Barrels 9 project from thelens-carrying plate. A slide Ill extends .forwardly fromfthe barrels'and supports a view carrier I I. The View carrier as placed in thetargets in Fig. 1. The person beingtested has the targets presented toboth eyes, but the dots are presented to his right eye only, andconsequently it is possible to obtain the correct visual acuity of theright eye alone, and this visual acuity of tie right eye.is obtainedwith the left eye operating in its normal manner.

dots 'as arranged in the views in Fig. 3 are shifted f from the positionof lthe dots in the right eld shownin'Fig. 2 so that the person beingtested has no check as to the sequence of the dots with reference to histest of the right eye.

' 'Ihe ophthalmologist in making the test can, with these views, byshifting one to the other, get quite a denite response from thepersonbeing tested, and this is true even though the personbeingtestedisayoungchildoranilliterateperson who may not be able todescribe the different symbols such 4as letters presented in theordinary tests, because .it is only necessary for the person beingtested to indicate as 'each target is presented, which square containsthe dat. This can be 'indicated' lby merely pointing or by simpledescription so that the ophthalmologist isvery sure to get a correctcheck from the response of the personbeing tested. It also assures notonly a normal te'stoi visual acuity where both eyes are cooperating inthe result, butalso a test of each 'individualeye operating under normalconditions with both eyes seeing.

This method and apparatus also makes it possible to carry on the testunder-all kinds of condie tions as in comparatively small rooms wherespacer would makethe ordinary methods impossible. and

targets beingofsimilar form.-

it provides a simple, compact apparatus that can be readily transported`for use so that a single apparatus can be readily used in variouslocations, as. for instance, where it is desired to conduct tests ofpupils in different places, such as schools. and workmen in shops. wheremass tests may be I demrable. i

What I claim as new is: y

1. A stereoscopic view having thereon a seriesoftestcharactersvaryinginsizeinadenite stepped size relation, eachcharacter having a size l0 of pre-established acuity value, the sizeshaving a range including test characters perceptible and test charactersimperceptible to an average eye.

2 A stereoscopic photographically formed view having test charactersvarying in size in a denite age sizes of equal sized object charactersat dennite stepped distances, each character having a size ofpre-established acuity value, the sizes having a range including testcharacters perceptible and test characters imperceptible to an averageeye.

3. A stereoscopic view having thereon testcharactersvaryinginsizeinadeilnitesteppedsise relation, each characterhaving a size of preestablished acuity value, the sizes having a rangeincluding test characters perceptible and test characters imperceptibleto an average eye.

4. A pic photographically formed viewhavingtestcharactersvaryinginsizeinadeiinite 30 stepped size relation,each character being located in a target and differently located indifferent targets corresponding to visual image sizes of equal sizedobject characters at deiinite steppeddistanceseaehcharacterhavingasizeo!s pre-established acuity value, the sizes having a range including testcharactersperceptible and test 'characters imperceptible to an averageeye.

5. A stereoscopic .view having thereontest characters varyingin sizein-a dennite stepped size 40 `relation, each character having a size otpreestablished acuity value. the sizes having a range including testcharacters perceptible and test characters imperceptible to an averageeye. the

45 REUEL A.

1 8A stepped size relation corresponding to visual im-

